st170 co2 sensor

my engine management light has come on for no aparent reason so i had my frend plug his diagnostics machine in and it come up with co2 sensor but does any one know how to check if that really is the problem as other people have said it could be my mass air flow sensor as there on the same loom? can any one help me????

[quote name='SuperSpecST' date='Sep 23 2009, 04:36 PM' post='44046']Do you have a standard exhaust? Some performance exhausts cause egm lights to come on. overfuelling when cold. More than likely to be lamda sensor though. Cheap and easy to replace.[/qu

Hi thank I have got a cat back system at the moment but i have had it on there about 8 months with no problem but also have a k&n induction kit on it which does not look very clean so my friend thinks i should try cleaning all the throttle body and air filter as the air to fuel ratio may be out. Really don't know where to start with this one lol. But thank you all very much for the replies.